Feed for aquatic species

ABSTRACT

The invention relates to a feed for aquatic species and crustaceans, in particular marine species and fry thereof. The feed described comprises proteins, lipids and additional, optional components, and is characterized in that the lipids are one or more marine oils and/or vegetable oils treated by urea and/or other amines or amides, to provent degradation due to oxidation (oxidative stress).

This invention relates to a feed for aquatic species including fry.

A problem for the aquaculture industry has been degradation and lowquality of the fat components in the feed due to oxidation. This problemhas previously been focused on farming of salmonids.

When marine fat, which is the main fat source in fish feed, reacts withoxygen, firstly primary oxidation products like peroxides are formed.The level of primary oxidation products is normally analysed as peroxidevalue. Peroxides from polyunsaturated fat are unstable and easilydegraded, resulting in transformation to secondary oxidation products.

Secondary oxidation products are a complex group of compounds includingaldehydes and ketones. To quantify the amount of secondary oxidationproducts the anisidine value is measured. The anisidine value is theintensity of a colour that develops during reaction between the reagentanisidine and aldehydes in the fat. The anisidine value is given withoutdenomination.

The level of oxidation in a fat is often given as totox-value. Thetotox-value is two times the peroxide value added with the anisidinevalue.

In feed for salmonids oils having low totox-values should be used Inorder to secure optimal growth for the fish.

In Norwegian Patent No. 309795 (corresponding to International patentapplication No. WO 00/01249) in the name of the present Applicant, amethod for stabilising vegetable and animal oils by treating the oil byurea and optionally one or more antioxidants, and a feed for salmonidscomprising inter alia oils treated by the said method are disclosed.Norwegian Patent No. 311041 (corresponding to International patentapplication No. WO 01/46355) also in the name of the present Applicant,further discloses a method for stabilising similar oils by treatment ofone or more other amines or amides. In NO-309795 and NO-311041 it isreported that by producing astaxanthin-containing fish feed forsalmonids with oil produced according to said methods, the degradationof astaxanthin during extrusion of feed pellets is considerably reduced.

At the time when NO-309795 and NO-311041 were filed, the aquacultureindustry was focused on farming of salmonids. The aim of the saidinventions was to reduce the degradation of astaxanthin and similarpigments, the most expensive components of fish feed. Now, however,other marine species have also become an object of the aquacultureindustry. These species, like cod and halibut, face the fish farmingindustry with new challenges. Feed for these species normally does notcontain significant amount of carotenoids like astaxanthin orcanthaxanthin. However, so far it seems as if these species are moredifficult to raise with optimum health and growth. One problem isrelated to low survival and low growth rate of fry and small fish.

In production of such marine species breeding of fry is a problem. Themortality of the fry is very high. In addition the rate of weight gain,especially of small fish, is lower than desired. One reason for this isthat the fish is sensitive to oxidative stress. When the fish is fed ahighly oxidized feed, the oxidative stress becomes high.

Thus, it is desirable to have access to a feed for the marine speciesand fry thereof where the oxidative stress of the feed is minimal.

The present invention is in a surprising manner able to provide a feedmore suitable for marine species and fry in particular, than previouslyknown feed.

The essential features of the present invention are given in theaccompanying claims.

A person skilled in the art will realize that a feed according to thepresent invention will be useful for all aquatic species andcrustaceans.

A feed for aquatic species including fry, containing lipids thatcomprises one or more marine oils and/or vegetable oils treated by ureaand/or other amines or amides and optionally one or more antioxidants isdisclosed in the present invention.

The above-mentioned amines and amides are defined by the generalformula:

wherein each of R1, R2 and R3 are independently chosen from H,C₁-C₁₀-alkyl, C₂-C₁₀-alkenyl, or RC(O)— or RN(H)—C(O)—C(O)— where R isH, C₁-C₁₀-alkyl or C₂-C₁₀-alkenyl, or R′N(H)—C(O)— where R′ isC₁-C₁₀-alkyl, C₂-C₁₀-alkenyl, or H if at least two of R1, R2 and R3 aredifferent from H.

According to one embodiment of the invention oils are heated in presenceof urea and/or other amines or amides, preferably above the meltingpoint of the nitrogen containing compound(s) and preferably kept at thistemperature for a time period of approximately 20-30 minutes, and one ormore antioxidants may be added. According to another embodiment of theinvention the oil is reacted with an aqueous mixture of 0.1-50% of ureaand/or other amines or amides, preferably 0.5-5% of urea and/or otheramines or amides. The preferred antioxidants are tocopherol and/orascorbic acid, and tocopherol and/or ascorbyl palmitate.

The invention also discloses the use of one or more marine oil and/orvegetable oil treated by urea and/or other amines or amides andoptionally one or more antioxidants for production of a feed for marinespecies including fry, which reduces degradation of the feed with regardto oxidation.

A preferred feature of this invention is that the oil is treated withurea and/or other amines or amides and added to the feed before or afterextrusion. The oil is treated either by heating in the presence of thenitrogen containing compound(s), or by reacting with an aqueous mixtureof nitrogen containing compound(s). Preferably the urea and/or aminesand amides are removed from the oil, e.g. by filtration, before the oilis added to the feed.

Another feature of the invention is that the nitrogen containingcompound(s) is added directly to the feed mixture, either in an aqueousphase or in solid form.

The nitrogen containing compound(s) may however be added in a number ofways and not only directly to an oil. By production of a feed ureaand/or other amines or amides can be added for instance during theextruding, by vacuum coating, spray coating and by oil bath. Thenitrogen containing compound(s) can also be added in the water phase orin solid form.

A preferred nitrogen-containing compound according to this invention isurea.

Among the marine species, cod and halibut are among the species that areof interest in the aqua culture industry.

In the following the invention will be further explained by examples anda FIGURE. The examples are just meant to be illustrative and shall notbe considered as limiting.

FIG. 1 shows secondary oxidation products expressed in anisidine numberfor omega oils treated with fish meal. Results for oils pre-treated withurea and oils not pre-treated with urea are shown.

EXAMPLE 1

Fish feed is extruded according to a recipe identical to Example 7 ofNO-309795. The extruded and dried feed pellets are analysed by usingElectron Spin Resonance. This is a method for elucidating the presenceand relative concentration for free radicals. Free radicals areassociated with ongoing oxidation; i.e. a high level of free radicals ina sample is associated with a high oxidative stress of that sample.

Results: ESR (pp-amp) Fish meal and wheat flour 2.0 Fish meal and wheatflour plus 1.7 fish oil Fish meal and wheat flour plus 2.8 fish oil.Heated at 125° C. for 5 min. Pellets, commercial formula 2.8 Pellets,urea-treated oil in 1.7 extruder

The ESR-results (pp-amp) give an indication of the concentration of freeradicals in the sample. A high numerical number indicate a high level offree radicals. The mixture of fish meal and wheat flour used for thefish feed gave a numerical result of 2.0 on this relative scale. Whenfish oil was added, the value was 1.7. After heating a sample of thismixture for 5 minutes at 125° C., simulating extrusion, the value hadincreased to 2.8. This was identical to the value after extrusion anddrying for feed pellets produced from the same mixture of meal, flourand oil. However, when the oil was substituted with an oil treated withurea according to the present invention, the value was 1.7 also afterextrusion. Surprisingly, the extrusion process had not resulted in anincrease in free radical activity of the dried pellets.

This shows that the present invention gives a feed that reduces theoxidative stress of a is feed composition.

The positive effect of the invention in showing a reduced oxidation offish feed can be shown by storing samples of feed in an atmosphere ofoxygen, and under increased pressure, with continuous recording ofoxygen consumption. The oxygen consumption is lower when an oilaccording to the present invention is used, compared to feed producedwith untreated oil.

EXAMPLE 2

A South American fish oil intended for fish feed (“omega oil”) mixedwith 20% (low temperature) LT fishmeal was heated to 60° C. withstirring. The oil was left for 30 minutes.

Initially the oils treated in this way (control) had an anisidine numberof 20.

For the aliquots of this oil treated according to NO-309795 (i.e.;heated with urea, cooled, and filtrating off the urea) the initialanisidine numbers were 2. As can be seen in FIG. 1, the anisidine numberof the control is rapidly reduced. It is assumed that this is due to areaction between amino acids/protein compounds and carbonyl compounds(i.e. secondary oxidation products), and that a similar reaction takesplace during feed production. It is further assumed that this isunfavourable for the value of the feed, which again indicates thatcommonly manufactured feed gives disadvantageous effects. Commerciallyavailable feed makes the proteins less bioavailable for the fish and/orthey decompose in the intestine of the fish and thereby secondaryoxidation products are released.

Wild fish do not experience the problems mentioned above, as wild fishdo not eat oxidized feed.

By the feed according to the present invention, the oxidation problemsnearly are solved. The present invention provides a feed of improvedquality.

The main object of the present invention is to provide a feed for marinespecies, included fry, where the oxidative stress of the feed due to fatoxidation is minimal. By treating the marine and/or vegetable oils inthe feed by urea and/or other amines or amides as given above, thisobject is fulfilled. The feed according to the present invention is dueto its minimal oxidative stress particularly suitable for marine speciesand fry. It is assumed that oxidative stress is one reason for thehealth problems, low survival and growth rate of fry and small fish. Byfeeding a feed according to the present invention to these species, fishof improved quality with regard to health, growth and survival areobtained. The possibility by using a feed with a minimal oxidativestress given by the present invention is a very important contributionwithin farming of marine species in the aquaculture industry.

Furthermore, heart rupture is a survival/health problem for salmonidsand other farmed fish species. This particular health problem is assumedoccur due to oxidative stress in the feed. Thus, using the feedaccording to the present invention is suitable also for salmonids inorder to reduce the heart rupture problems of the fish.

By applying the method for stabilising vegetable and marine oils asdisclosed in NO-309795 and NO-311041, lipids causing oxidative stress infeed for marine species are obtained. In this way a feed for marinespecies and fry in particular, that causes less oxidative stress to thefish is obtained. This feed is also suitable for salmonids, particularlyfor reducing the occurrence of heart rupture.

The present invention implies an improved solution to the breedingproblem of fry of marine species as described above. A satisfactorysolution to this problem has previously not been found.

The person skilled in the art will realise that similar problems relatedto non-optimal growth and health due to oxidative stress from the feedwill be relevant to all aquatic species, not only fish.

1-6. (canceled)
 7. A method of farm-raising fish that are still in thegrowing stage, which comprises feeding the fish a feed that comprises25-70% by weight of proteins, 5-60% by weight of lipids, 0-40% by weightof carbohydrates, and 0-15% by weight of one or more additionalcomponents, wherein the lipids comprise at least one oil selected fromthe group consisting of marine oils and vegetable oils, wherein saidat-least-one oil has been treated with at least one nitrogen-containingcompound selected from the group consisting of urea and compounds of thegeneral formula

wherein each of R1, R2, and R3 is independently a radical selected fromthe group consisting of H, C₁₋₁₀ alkyl, C₂₋₁₀ alkenyl, RC(O)—,RN(H)—C(O)—, and RN(H)—C(O)—C(O)— wherein R is H, C₁₋₁₀ alkyl, or C₂₋₁₀alkenyl, with the proviso that at least one of R1, R2, and R3 is otherthan H, the amount of said at-least-one nitrogen-containing compoundbeing sufficient to reduce the oil's susceptibility to being degradedthrough oxidation, and the amount of said at-least-one oil in the feedbeing sufficient to enhance the feed's ability to either improve thesurvival rate of the fish or improve the growth rate of the fish.
 8. Themethod of claim 7, wherein the at-least-one oil has been treated withthe at-least-one nitrogen-containing compound either by (a) heating amixture of the oil and the nitrogen-containing compound or (b) reactingthe oil with a mixture of the nitrogen-containing compound and water. 9.The method of claim 8, wherein, in treatment (a), the mixture is heatedto a temperature above the melting point of the nitrogen-containingcompound for a time period of approximately 20-30 minutes.
 10. Themethod of claim 9, wherein, in treatment (b), the aqueous mixturecontains 0.1-50% by weight of the nitrogen-containing compound.
 11. Themethod of claim 10, wherein the treating of the oil occurs before theoil is added to the feed, and wherein the treated oil, prior to beingadded to the feed, is subjected to a separation step by which unreactednitrogen-containing compound is first removed from the oil.
 12. Themethod of claim 7, wherein the at-least-one oil is treated with theat-least-one nitrogen compound while the oil is in admixture with theother components of the feed.
 13. The method of either of claims 11 or12, wherein the fish comprises fry.
 14. The method of either of claims11 or 12, wherein the feed also comprises at least one or moreantioxidants.
 15. The method of either of claims 11 or 12, wherein thefeed does not contain a significant amount of carotenoids.
 16. Themethod of either of claims 11 or 12, wherein the feed does not contain asignificant amount of carotenoids, the feed also comprises at least oneor more antioxidants, and the fish comprise fry.
 17. The method of claim7, wherein the fish is selected from the group consisting of cod andhalibut.
 18. The method of claim 8, wherein the fish is selected fromthe group consisting of cod and halibut.
 19. The method of claim 9,wherein the fish is selected from the group consisting of cod andhalibut.
 20. The method of claim 10, wherein the fish is selected fromthe group consisting of cod and halibut.
 21. The method of claim 11,wherein the fish is selected from the group consisting of cod andhalibut.
 22. The method of claim 12, wherein the fish is selected fromthe group consisting of cod and halibut.
 23. The method of either ofclaims 21 or 22, wherein the fish comprises fry.
 24. The method ofeither of claims 21 or 22, wherein the feed also comprises at least oneor more antioxidants.
 25. The method of either of claims 21 or 22,wherein the feed does not contain a significant amount of carotenoids.26. The method of either of claims 21 or 22, wherein the feed does notcontain a significant amount of carotenoids, the feed also comprises atleast one or more antioxidants, and the fish comprise fry.